A control circuit and method for a PWM voltage regulator combine a high frequency feedback technique with a constant on-time or constant off-time topology to improve the transient performance of the PWM voltage regulator. The PWM voltage regulator generates a constant on-time or constant off-time depending on a current for generating a PWM signal, and dynamically adjusts the current according to the droop-voltage at its output during a transient period. Therefore, the PWM voltage regulator boosts its transient response without any threshold for load step detection.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A control circuit for providing a PWM signal for a PWM voltage regulator to convert an input voltage into an output voltage, the control circuit comprising: a constant-time generator generating a constant time to determine a constant on-time or a constant off-time of the PWM signal; and a high-frequency feedback controller connected to the constant-time generator, operative to establish a high-frequency feedback loop responsive to transient of the PWM voltage regulator, to adjust the constant time instantly; wherein the high-frequency feedback controller comprises a bypass capacitor parallel connected to a serially connected quick response capacitor and quick response resistor; wherein the constant-time generator comprises: a capacitor; a current-controlling current source connected to the capacitor, for determining a second current according to a first current to charge the capacitor; a switch connected in parallel to the capacitor, for resetting the capacitor; and a comparator connected to the capacitor, for comparing a voltage at the capacitor to a reference voltage to generate the PWM signal.
2. The control circuit of claim 1 , wherein the high-frequency feedback controller comprises a high-frequency signal filtering circuit for establishing the high-frequency feedback loop.
3. The control circuit of claim 2 , wherein the high-frequency signal filtering circuit comprises a high-pass filter.
4. The control circuit of claim 3 , wherein the serially connected quick response capacitor and the quick response resistor are connected between the constant-time generator and an output terminal of the PWM voltage regulator.
5. The control circuit of claim 1 , wherein the high-frequency feedback controller adjusts the first current to thereby adjust the constant time.
6. The control circuit of claim 1 , wherein the high-frequency feedback controller adjusts the second current to adjust the constant time.
7. The control circuit of claim 1 , further comprising a resistor connected to the constant-time generator for generating the first current according to the input voltage.
8. A control method for providing a PWM signal for a PWM voltage regulator to convert an input voltage into an output voltage, the control method comprising steps of: A.) generating a constant time to determine a constant on-time or a constant off-time of the PWM signal; and B.) establishing a high-frequency feedback loop responsive to transient of the PWM voltage regulator, to adjust the constant time instantly; wherein the step B comprises a step of extracting a high-frequency signal through the high-frequency feedback loop; wherein the step A comprises steps of: determining a second current according to a first current; generating a linearly varying voltage according to the second current; and comparing the linearly varying voltage with a reference voltage to generate the PWM signal.
9. The control method of claim 8 , wherein the step B comprises a step of adjusting the first current to adjust the constant time.
10. The control method of claim 8 , wherein the step B comprises a step of adjusting the second current to adjust the constant time.
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June 1, 2012
December 23, 2014
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